Direct-current electricity meter



Aug. 7,1928. 1,619,712 s. 2. DE FERRANTI, ninac'r 01111112111 mic-1111:1111 11111311' filed Feb. 10, 1925 4 Sheets-Sheet 1 Aug. 7,1928. 1,619,712

, s z. DEFERRANTI nnmcw CURRENT ELECTRICITY METER Filed Feb.10, 1925 4 Sheefs-Sheet 2 Aug. 7, 1928. 1,679,712.

s. z. DE FERRANTI DIRBG'I. CURRENT ELECTRICITY IBTER Filed Febrlo, 1925 4 Sheets-Sheet 3 Aug. 7, 1928. 1,679,712 v s. 2. DE FERRANTI DIRECT CURRENT ELECTRICITY METER Filed Feb. 10, 1925 {Sheets-Sheet 4 fa will electricity meters til : B-B of Figure 1;

Patented Aug. 7, 1928.

LIMITED, or HoLnmwooD, ENGLAND.

DIRECT-CURRENT ELECTRICITY METER.

Application filed February This invention relates to direct current .of the type including a disc rotor immersed in a mercury bath and so carried upon a spindle which gears it to the measuring train asto be rotatable between the poles of oneor more permanent The chief advantage which my invention provides is the ability to secure ready access to the spindle and rotor and theiability to erect or dismantle a complete unit without disturbing the magv netic circuit.

Certain other advantages will appear from consideration of the description given below.

The accompanying drawings illustrate one example of carrying the invention into effect,

1 v y {region of the studs so asto 'form slightly 7 outstanding bosses with chamfered edges. 1 r

The footstep bearing comprises'a jewel in which 2- Figure 1 is a front elevation; Figure 2 is a section on the staggered line Figure 3 is a vertical GC of Figure 1; I .c

Figure 4;;is a horizontal sectionon the staggered line.A-A ofFigure 1;

Figure 5 is a horizontal section onthe line D-D of Figure 2.

section 'on the line The upper half of Figure 6 is ahorizonp E.,-E of "Figure 3; 1

tal section on theline and the lowerhalf of Figurefi is a horizontal section on theline F F of Figure a Figure 7 is a diagrammatieview indicating the current paths through theometer;

Figures 8, 9 and 10illustrate front elevational, side spectively of the compensating magnets;

Figures 11, 12 and 13 llustrate a method 1 of withdrawing the lower bearing block, and

Figures 14 and 15 illustrate a method of removal of the magnets j In carrying the invention into effect in one form by way of example as applied to a meter with disc rotor, I provide a nonmagnetiometal frame a formed with a bed for the mercury bath and for two C-shaped permanent magnets b,- b which straddle the loath. The bath itself is circular and is the rotor and spindlev'as elevational and plan viewsvre f 19 tending to 10, 1925, Serial No- 8,279, a.nd in Great Britain'March 3 1924.

moulded in three. portions of which: the upper and lower portions 0, d constitute the top and bottom members of the bath re spectlvely and'the third e constitutes the re- L movable part whose function will be ex- SEBASTIAN zranrnn realm-N021, or nonmnw'oon; ENGLAND, ASSIGNOR 'ro 'rEnRAn'rI;

plained below, The upper and lower bath portions are each furnished with faced contiguous surfaces gether amercury-tight joint at f is'secured, varnish or vother adhesivema'terial being employed at this joint, if desired. f

The upper bath member a is rovidedwith" a pair of soft iron studs g, g isposed :equiv distant from thexcentre ona diameter and the lower bathmember is similarly provided a at h, h. These studs, which constitute pole v pleces, are moulded in positionand each is so that when clamped to-e,

of such length asto. project somewhat above and below the boundaries, of thebath. The 7 studs also project slightly within-the bath and the latter isthickened slightly'in the set in-a block lo which-isslidable radially in a groove formed .in-the bottom member d of the bath and the usual loose collar m embodying packing n is provided to enable sea ling-of-the mercury outlet and locking of thespindle during tra'nsitQ Thelinner bath proper andiconforms to; the curvature of the removable portione of the bath. 1

v This. mechanism for'eife'cting' the lockin "of the spindle against its upper bearing during transit is effected 'bymeansrofua'" cranked memb'eri 18 whose forked end en-. gages a groove'in the loose collar,-the spring 1 lift the member 18 and bein frestrained b o-the pin eccentrically mounted on the spin; le 21; Whenthe spindle 'occupies the position shown in Figure 3c the member 18 is not-bear against the .collarf'22 fixed to the ,meter spindle, but when the'spindle is pardrawn down so-that the cap'm does tially, rotated the spring 19'draws up the "cranked; member and forces the cap m} against thefconical internal surface of the collar 22, thus both lifting the spindle off single short length of its footstep bearing and effecting a sealing of the mercury chamber.

It will be understood that as the member 18 is guided in the frame a and not by the meter casing, there is no necessity to provide insulation between the member and the easing other than that which separates the meter mechanism as a whole from the casing.

A suitable non-sticking packing piece 1 is preferably interposed between the block 10 and the notched faces against which it is clamped.

The removable part a of the bath is formed somewhat of sector shape and is adapted to be clamped against appropriately shaped faces on the bath proper and on the front of the block referred to above, a suitable nonsticking packing piece 8 preferably being interposed also at this joint.

The two C-shaped permanent magnets b, b are clamped to two suitable faces on the nonmagnetic frame a-so as to register with the soft iron pole pieces 9, h moulded in the bath and each is removable without disturbing any other-partof the meter. The polarity of the two magnets is such that unlike poles are formed at the two pole pieces in the upper wall of the bath. Current is led into the bath by way of three studs t, u, '2) let into the periphery of the bath, the central stud wbeing coupled to one end of a resistance w whose other end is connected to both the remaining studs. This resistance acts in the manner of a potentiometer when the point thereon at whic'hconnection to the external circuit is established is varied and means are thus provided whereby the constant of the meter may be adjusted. Current is similarly led out of the bath after passage through the mercury and disc, i. e. between the air gaps of both magnetic circuits. q

Each resistance comprises conveniently a wire 10 (of material possessing considerable specific resistance) which is supported by the leads terminating in the studs z; and o and in the stud u. Disposed parallel to each resistance is a single short length of copper as which in turn is supported by its attachment to a meter terminal 3 in the terminal blocks. A slider 2 which may be clamped in any desired posi tionalong the pair of wires is provided and V constitutes the lead-in and lead-out point of each resistance unit respectively.

This construction is indicated diagrammatically in Figure 7 and in action it will be appreciated that two paths through the meter are open to the current as indicated by the arrows 1) the path from the stud 21 to the corresponding stud at the opposite side of the bath and (2) the paths which are chords to the circumference of the bath.. The current passingby path (2) is not able to the two magnet poles above the disc 3 and further coils 9 disposed between the two cores l0 and 11 respectively, in such manner and so connected that when energized by the load current they divert some of the flux from the operative air gaps in the bath,

whilst'not, however, varying the flux within the steel constituting nets.

It will be noted that air gaps 12 areprovided in order to provide the necessary reluctance in the magnetic shunt path which the cores 10, 11 constitute.

Although variation of the main flux in the air gaps within the bath affects both the driving and the braking torques, since each main flux serves both to drive and to brake effective compensation is possible on account of the fact that a given variation of these fluxes causes a larger variation in braking torque than in driving torque.

It will also be seen that the actual'path of the flux traversing the steel of the ma nets is not changed bv diversion of someoi' the main flux from the air gaps within the meter bath.

The terminal block a comprises insulating material which is screwed to the non-magnetic frame a by two screws 4 i and which carries embedded therein suitable terminals.

This terminal block is formed with prothe permanent magjecting bosses 13 which register with corresponding holes in the meter casing and thus hold securely in position within the casing the base of the whole metermechanism as a The detachable sector-like bath portion 6* is removed (together with its packing piece, if fitted) by releasing the saddle 5, the top a'butments are sloped spindle bearing 7 is raised clear of the top spindle pivot and the disc 3 Withdrawn sideways. This sideways movement withdraws the footstep which the block 71: supporting itis fitted and in order to avoid the risk of bending the bottom spindle pivot'or of damaging the bearing itselfT prefer to employ a special tool in this operation. This tool, which is indicated in Figureslll, 12 and 13, comprises a distance block 23 through a hole in which a screwed. spindle 24 is fitted, the spindle being adapted to enter a threaded hole 6 in the foostep bearing block 76. Thus, when the spindle is screwed homev in the hole 6 the distance block rests below the disc in light contact with theunder surface thereof (see Figures 11 and 12) and provides such purchase as will enable the sidewise pull to be exerted simultaneously upon the disc 3 and bearing block is. lVhcn removed the parts occupy the position shown in Figure 13.

It will be noted that these operations do not involve any disturbance of the leading-in and leading-out device for the meter-constant adjustment. 7

j The permanent magnets I), Z) in accordance with the present invention may be magnetized and even aged apart from the meter, being afterwards assembled inposition without disturbing the flux in thesteel. This is effected conveniently by the provision of soft iron keepers which are ,kept in position during the magnetizing process (and during the ageing process if then carried out).

Theke eper as is illustrated in Figures 14 and 15 conveniently comprises a U-shaped member 25, the extremities of whose limbs are shaped to correspond exactly with the portions of the soft iron pole pieces g, g and h, h which project above and below the meter bath. The cross-sections of the limbs and of the base of the keeper are such that the keeper may be slid between the'extremities of the magnet in close contact therewith without altering the flux density ordirection in the steel magnet. Thus, in order say to remove a magnet from the meter at any time, it is merely necessary to apply the keeper 25 to the soft iron pole piece projections (with the keeper straddling part, of the bath), whereupon the magnet may be slid on to the keeper into the position shown in dotted line in Figure 15 and removed, together with the magnet. Thus there is no alteration in the magnitude or direction of the flux in the steel of the magnets.

Alternatively, the extremities of the magnet may be furnished with soft iron pole pieces and a soft iron keeper applied so as to straddle the bath and to contact with the sides of these pole pieces. Under these circumstances, although bearing along the groove in.

electricity meter of latter which is retained in the gap separating the extremities of the scribed including a no sliding of the magvrotor therein, a laterally detachable portion 1. An electricity meter of the type ide scribed including a mercurybath,

a steel permanent magnet, soft iron pole pieces, the'latter being embodied'in the said bat-h so as to provide an operative air gap, said meter including means for compensating the drooping characteristic of the percentage-error-load curve, which means comprise a magnetic shunt adapted to coact With said soft iron pole pieces in order to divert some of the main flux from the operative air gap without changing the distribution of the flux in the steel constituting the permanent magnet.

2. Means for adjusting the constant of an electricity meter of .thetype described including a mercury bath, a pair of lead-in contacts and an intermediate lead-in contact associated with the mercury bath, an

electrical connection between said pair of contacts, an electr cal connection possessing resistance from the intermediate contact to said interconnected pair of contacts, and a movable clamping piece coacting with said resistance connection and clamped in alternative positions thereon whilst in continuous electrical connection with the lead-in terminal of the meter.

.3. Means for adjusting the constant of an the type described including amercury bath, a pair of lead-in contacts and an intermediate lead-in concapable of being tact associated with the mercury bath, an

electrical connection betweensaid pair of,

contacts, an electrical connection possessing resistance from the intermediate contact to said interconnected pair of contacts, a movable clamping piece coacting with said resistance connection and capable of being clamped in alternative 1 positions thereon whilst in continuous electrical connection with the lead-in terminal of'the meter and a similar set of contacts, resistance connection and a clamp in respect of the lead-out terminal of the meter.

4. An electricity meter of scribed including a mercury rotor therein, a laterally detachable portion for said bath and means enabling the rotor spindle and disc as a complete unit to be removed from Or erected in running position while maintaining constant in magnitude and direction the flux of the magnetic circuit.

5. An electricity meter of the type demercury bath, a disc the type de bath, a disc for said bath and a laterally detachable foot-step bearing in said bath for the spindle of said disc rotor, thus enabling the rotor' spindle and disc as a complete unit together with the footstep bearing to be removed from or erected in running position while maintaining constant in magnitude and direction the magnetic flux.

6. An electricity meter as claimed in claim, 2, including also soft iron pole pieces moulded into said mercury bath.

7. An electricity meter of the type described including a nonmagnetic frame upon which a mercury bath, top and bottom spindle bearings, rotor spindle, permanent magnet and terminal block are supported to form a unit which readily may be insorted and removed from the containing case.

8. Means for enabling a permanent magnet to be placed in operative position and to be removed therefrom with maintenance of the magnetic flux in the steel unchanged in magnitude and direction, which means comprise a pronged keeper of soft iron, whose prongs are adapted to abut pole pieces associated with said permanent magnet, the keeper being of thickness corre sponding to that of the pole pieces and with a cross-sectional area at least equal to that of the magnet.

In testimony whereof I havesigned my name to this specification. 1 SEBASTIAN ZIANI DE FERRANTI. 

